Vulnerabilities > CVE-2018-5244 - Improper Restriction of Operations within the Bounds of a Memory Buffer vulnerability in XEN

047910
CVSS 4.9 - MEDIUM
Attack vector
LOCAL
Attack complexity
LOW
Privileges required
NONE
Confidentiality impact
NONE
Integrity impact
NONE
Availability impact
COMPLETE
local
low complexity
xen
CWE-119
nessus

Summary

In Xen 4.10, new infrastructure was introduced as part of an overhaul to how MSR emulation happens for guests. Unfortunately, one tracking structure isn't freed when a vcpu is destroyed. This allows guest OS administrators to cause a denial of service (host OS memory consumption) by rebooting many times.

Common Attack Pattern Enumeration and Classification (CAPEC)

  • Buffer Overflow via Environment Variables
    This attack pattern involves causing a buffer overflow through manipulation of environment variables. Once the attacker finds that they can modify an environment variable, they may try to overflow associated buffers. This attack leverages implicit trust often placed in environment variables.
  • Overflow Buffers
    Buffer Overflow attacks target improper or missing bounds checking on buffer operations, typically triggered by input injected by an attacker. As a consequence, an attacker is able to write past the boundaries of allocated buffer regions in memory, causing a program crash or potentially redirection of execution as per the attackers' choice.
  • Client-side Injection-induced Buffer Overflow
    This type of attack exploits a buffer overflow vulnerability in targeted client software through injection of malicious content from a custom-built hostile service.
  • Filter Failure through Buffer Overflow
    In this attack, the idea is to cause an active filter to fail by causing an oversized transaction. An attacker may try to feed overly long input strings to the program in an attempt to overwhelm the filter (by causing a buffer overflow) and hoping that the filter does not fail securely (i.e. the user input is let into the system unfiltered).
  • MIME Conversion
    An attacker exploits a weakness in the MIME conversion routine to cause a buffer overflow and gain control over the mail server machine. The MIME system is designed to allow various different information formats to be interpreted and sent via e-mail. Attack points exist when data are converted to MIME compatible format and back.

Nessus

  • NASL familyMisc.
    NASL idXEN_SERVER_XSA-253.NASL
    descriptionAccording to its self-reported version number, the Xen hypervisor installed on the remote host is affected by a guest-to-host denial of service vulnerability. Note that Nessus has checked the changeset versions based on the xen.git change log. Nessus did not check guest hardware configurations or if patches were applied manually to the source code before a recompile and reinstall.
    last seen2020-06-01
    modified2020-06-02
    plugin id105775
    published2018-01-12
    reporterThis script is Copyright (C) 2018-2019 and is owned by Tenable, Inc. or an Affiliate thereof.
    sourcehttps://www.tenable.com/plugins/nessus/105775
    titleXen vcpu Destruction Handling Memory Exhaustion Guest-to-Host DoS (XSA-253)
    code
    #
    # (C) Tenable Network Security, Inc.
    #
    
    include("compat.inc");
    
    if (description)
    {
      script_id(105775);
      script_version("1.5");
      script_cvs_date("Date: 2019/11/08");
    
      script_cve_id("CVE-2018-5244");
      script_bugtraq_id(102433);
      script_xref(name:"IAVB", value:"2018-B-0013");
    
      script_name(english:"Xen vcpu Destruction Handling Memory Exhaustion Guest-to-Host DoS (XSA-253)");
      script_summary(english:"Checks 'xl info' output for the Xen hypervisor version.");
    
      script_set_attribute(attribute:"synopsis", value:
    "The remote Xen hypervisor installation is missing a security update.");
      script_set_attribute(attribute:"description", value:
    "According to its self-reported version number, the Xen hypervisor
    installed on the remote host is affected by a guest-to-host denial
    of service vulnerability.
    
    Note that Nessus has checked the changeset versions based on the
    xen.git change log. Nessus did not check guest hardware configurations
    or if patches were applied manually to the source code before a
    recompile and reinstall.");
      script_set_attribute(attribute:"see_also", value:"http://xenbits.xen.org/xsa/advisory-253.html");
      script_set_attribute(attribute:"see_also", value:"https://xenbits.xen.org/gitweb/?p=xen.git;a=summary");
      script_set_attribute(attribute:"solution", value:
    "Apply the appropriate patch according to the vendor advisory.");
      script_set_cvss_base_vector("CVSS2#AV:L/AC:L/Au:N/C:N/I:N/A:C");
      script_set_cvss_temporal_vector("CVSS2#E:U/RL:OF/RC:C");
      script_set_cvss3_base_vector("CVSS:3.0/AV:L/AC:L/PR:L/UI:N/S:C/C:N/I:N/A:H");
      script_set_cvss3_temporal_vector("CVSS:3.0/E:U/RL:O/RC:C");
      script_set_attribute(attribute:"cvss_score_source", value:"CVE-2018-5244");
    
      script_set_attribute(attribute:"exploitability_ease", value:"No known exploits are available");
      script_set_attribute(attribute:"exploit_available", value:"false");
    
      script_set_attribute(attribute:"vuln_publication_date", value:"2018/01/04");
      script_set_attribute(attribute:"patch_publication_date", value:"2018/01/04");
      script_set_attribute(attribute:"plugin_publication_date", value:"2018/01/12");
    
      script_set_attribute(attribute:"potential_vulnerability", value:"true");
      script_set_attribute(attribute:"plugin_type", value:"local");
      script_set_attribute(attribute:"cpe", value:"cpe:/o:xen:xen");
      script_set_attribute(attribute:"stig_severity", value:"I");
      script_end_attributes();
    
      script_category(ACT_GATHER_INFO);
      script_family(english:"Misc.");
    
      script_copyright(english:"This script is Copyright (C) 2018-2019 and is owned by Tenable, Inc. or an Affiliate thereof.");
    
      script_dependencies("xen_server_detect.nbin");
      script_require_keys("installed_sw/Xen Hypervisor", "Settings/ParanoidReport");
    
      exit(0);
    }
    
    include("audit.inc");
    include("global_settings.inc");
    include("install_func.inc");
    include("misc_func.inc");
    
    app_name = "Xen Hypervisor";
    install  = get_single_install(app_name:app_name);
    if (report_paranoia < 2) audit(AUDIT_PARANOID);
    
    version         = install['version'];
    display_version = install['display_version'];
    path            = install['path'];
    managed_status  = install['Managed status'];
    changeset       = install['Changeset'];
    
    if (!empty_or_null(changeset))
      display_version += " (changeset " + changeset + ")";
    
    # Installations that are vendor-managed are handled by OS-specific local package checks
    if (managed_status == "managed")
      audit(AUDIT_INST_PATH_NOT_VULN, app_name, display_version, path);
    
    fixes['4.10']['fixed_ver']           = '4.10.1';
    fixes['4.10']['fixed_ver_display']   = '4.10.1-pre (changeset a87ec48)';
    fixes['4.10']['affected_ver_regex']  = '^4\\.10\\.';
    fixes['4.10']['affected_changesets'] = make_list("9dc5eda", "135b67e",
      "682a9d8", "19dcd8e", "e5364c3", "e2dc7b5", "c8f4f45", "4150501",
      "ab7be6c", "f3fb667");
    
    fix = NULL;
    foreach ver_branch (keys(fixes))
    {
      if (version =~ fixes[ver_branch]['affected_ver_regex'])
      {
        ret = ver_compare(ver:version, fix:fixes[ver_branch]['fixed_ver']);
        if (ret < 0)
          fix = fixes[ver_branch]['fixed_ver_display'];
        else if (ret == 0)
        {
          if (empty_or_null(changeset))
            fix = fixes[ver_branch]['fixed_ver_display'];
          else
            foreach affected_changeset (fixes[ver_branch]['affected_changesets'])
              if (changeset == affected_changeset)
                fix = fixes[ver_branch]['fixed_ver_display'];
        }
      }
    }
    
    if (empty_or_null(fix))
      audit(AUDIT_INST_PATH_NOT_VULN, app_name, display_version, path);
    
    items  = make_array(
      "Installed version", display_version,
      "Fixed version", fix,
      "Path", path
    );
    
    order  = make_list("Path", "Installed version", "Fixed version");
    report = report_items_str(report_items:items, ordered_fields:order) + '\n';
    
    security_report_v4(port:0, extra:report, severity:SECURITY_WARNING);
    
  • NASL familyGentoo Local Security Checks
    NASL idGENTOO_GLSA-201810-06.NASL
    descriptionThe remote host is affected by the vulnerability described in GLSA-201810-06 (Xen: Multiple vulnerabilities) Multiple vulnerabilities have been discovered in Xen. Please review the referenced CVE identifiers for details. Impact : A local attacker could cause a Denial of Service condition or disclose sensitive information. Workaround : There is no known workaround at this time.
    last seen2020-06-01
    modified2020-06-02
    plugin id118506
    published2018-10-31
    reporterThis script is Copyright (C) 2018-2019 and is owned by Tenable, Inc. or an Affiliate thereof.
    sourcehttps://www.tenable.com/plugins/nessus/118506
    titleGLSA-201810-06 : Xen: Multiple vulnerabilities (Foreshadow) (Meltdown) (Spectre)